Method of straightening wire rods of titanium and titanium alloy

A method of straightening a titanium or titanium alloy wire rod for an engine valve comprising the steps of:

• providing a titanium or titanium alloy billet, where the titanium ally is selected from the group consisting of .beta., .alpha.+.beta. or near .alpha. titanium alloy;
• hot rolling a titanium billet into a wire rod;
• winding the hot rolled wire rod into a coil;
• cold drawing the wire rod;
• cutting the wire rod to a predetermined length to obtain a bent wire rod;
• heating the bent wire rod to a straightening temperature T while both end portions of the wire rod are fixed to a holding device of a hot straightener and tension is given to the wire rod;
• applying a predetermined straightening elongation .epsilon. to the wire rod at the straightening temperature;
• maintaining heat at the straightening temperature T for a predetermined period of time;
• hot-straightening the wire rod under the condition that the straightening temperature T and straightening elongation .epsilon. satisfy the following expression (1)
• .epsilon.(T-400).gtoreq.100 (1)
• ceasing heating of the wire rod when a predetermined straightening elongation is applied to the wire rod;
• and
• cooling the wire rod while a tension is applied to the wire rod upon cessation of heating, thereby forming a straight titanium wire rod having less than 1 mm/m bending.